FR2621050A1 - IMPROVEMENTS RELATING TO A LEATHER TREATMENT PROCESS AND IMPROVED LEATHER THUS TREATED - Google Patents

Abstract

Disclosed is a method for treating leather to improve inhibition of chromium depletion and various other properties. This process consists of treating the leather with a dispersion of a polyester or a microcrystalline polyamide. This treatment is carried out during the tanning, re-chroming, retanning or dyeing stage.

Description

1 26221050

  Improvements relating to a treatment process

  leather and improved leather thus treated.

The present invention relates to

  improvements relating to a milking process

  leather, as well as improved leather thus treated. In the art, it is generally known that animal hides and skins are subjected to several chemical and physical treatments in order to impart the required physical and chemical properties to the leather and thus make it

  suitable for various applications.

  Since after skinning animals, hides and skins have a high content of water, degradable protein and impurities, they are susceptible to degradation and putrefaction. In order to avoid this degradation or this putrefaction, after having stripped the animal, the hides and skins are subjected to the stage of preservation by the salting technique. Then we submit the skins

  and salted leathers to a compressed purification process

  during the steps of soaking, leveling, de-

  leveling, jamming and juiceing, these purification stages being carried out before the stage

tanning.

  The tanning step consists of a

  chemical in which we use either

2 2 6 2 1 0 5 0

  plant extracts, or mineral tanning agents.

  In the tanning process in which mineral tanning agents are used, the cleaned skins and hides are subjected to the well-known step of chrome tanning treatment. This treatment consists in using chromium chloride or sulphate which, under acidic conditions, penetrates into the structure of the leather. The chromium salts form a complex with carboxyl groups of proteins during the later stage of basification. The chromium treatment stage is preferred to the treatment with plant extracts, because it confers better chemical and physical properties and, moreover, it makes it possible to improve the resistance to thermal hydrolysis and to microorganisms. Although chrome tanning is preferred, in practice it has been found that only 75% chromium binds to leather

  and that the remaining proportion, 25-30%, not-

  knows in the effluent. This loss or this exhaustion

  Chromium has serious drawbacks because it is generally believed that the higher the amount of chromium attached to leather, the better the chemical, physical and heat resistance properties. In addition, the loss of 25-30% of chromium is added to the final expenses already made for the process. Yet another drawback resides in the fact that the chromium leaving the matrix or the surface of the leather penetrates into the effluent and poses serious

pollution issues.

  In addition to chromium, in the art, other tanning agents have been suggested such as "Syntans" (= registered trademark for synthetic tannins) of chromium-aluminum,

3 2621050

  titanium or zirconium. Although these agents have been suggested, in the industry, chromium is still and is generally used

tanning agent.

  During the tanning step with plant extracts, hides and skins are treated with plant extracts and the treated leather thus obtained is generally known under the name

"EI tanned leather".

  After the tanning step by treatment with chromium salts, the treated leather is subjected to the basification step during which crosslinking of the chromium with the carboxyl group of collagen takes place. This treated leather is known in the art under the name "wet blue leather". Since a limited amount of chromium is attached to wet blue leather,

  this is subjected to the rechroming stage consisting of

  both in treatment with chromium salts and in basification so that more chromium can come

fix on the leather.

  Neutralize the wet blue leather at a pH of 4.5-5.6 so that it is ready to tackle the juice processing process

  oily and tincture. Neutralization is carried out

  tion to bring the surface charge of the leather from the cationic state to the anionic state, which, in other conditions, causes precipitation

  dyes and fatty juices on the surface.

  Then, the leather is subjected to the retanning step. The purpose of this retanning step is to impart specific properties to the leather. This retanning step fills the structure of the empty spaces, it corrects the variation 4 2 62 5 0 v in thickness, it equalizes surface defects and, moreover, it contributes to ensuring better

dye penetration.

  This retanning step is intended to improve the general feel, thickness, robustness, resistance to chemicals,

  heat resistance, ability to ef-

  flowering, richness and absorbing properties

  dyes. However, in practice,

  it has been found that these properties do not improve

  not laugh appreciably. We used a certain

  number of "Syntans" during the retan-

  swim. Among the types of "Syntans" used, there are those based on phenolformaldehyde, acid

  naphthalene sulfonic, acrylic and urea type-

  formaldehyde, chromium-aluminum and zirconium.

  Reactive fillers, mica and silica are sometimes used to impart specific properties. During or after the retanning step, the leather is also subjected to the dyeing and fatty juice treatment steps. We observed

  that the fat processing step improves

  has the properties of softness, robustness,

  of suppleness, stretch and flexibility.

  A main object of the present invention is to provide a method for the

  leather treatment to give it better

  their properties, namely a clear coloring tone, satisfactory penetration of dyes, lubrication of the grain, softness, suppleness, extensibility, flexibility

and robustness.

  Another object of the present invention is to provide a method for treating leather in order to give it better properties relating to the feel, the resistance to chemicals, the resistance to heat and the richness. Another object of the present invention is to provide a method for the treatment of leather, in order to prevent a significant depletion of chromium out of the treated leather and thus attenuate

  the problem of effluent pollution.

  According to the present invention, there is provided an improved method for treating leather by known steps including tanning, re-chroming, retanning and dyeing, this method being characterized by the step of treating leather with an aqueous dispersion

  polyamide and / or polyester.

  Specifically, according to the present invention, the tanning, rechroming, retanning and / or dyeing step is carried out in the presence of an aqueous dispersion of a material based on a polyamide and / or a polyester. Preferably, the particles of this polymer which are used in the dispersion, have a granularity of 2 microns and less. It has been found that particles of greater granularity do not effectively penetrate the pores of the leather. At the same time, it is understood that, when, in the present specification, reference is made to a dispersion containing these particles of polymers, particles of different granularities are also included, as well as the cases where the major part of these particles present in the dispersion have a granularity of 2 microns

and less.

  Surprisingly, it has now been found that such treatment with an aqueous dispersion of a polyamide and / or a polyester considerably improves the properties of the leather. Consequently, and in the case where such a treatment is carried out with the step of tanning with chromium and / or rechroming, the exhaustion of chromium outside the leather is significantly reduced, thus ipso facto increasing the fixation of chromium. Such an increase in the fixation of chromium or a reduction in its depletion constitutes an important advantage in that the properties relating to the feel, the thickness, the robustness, the resistance to chemicals and to heat, to the richness and absorption of dyes are greatly improved. Yet another advantage of equal importance is that, as a result of the reduction in chromium depletion, the amount of chromium in the effluent is reduced, attenuating

  thus pollution problems.

  If such a treatment is carried out with the polyamide and / or polyester dispersion during the retanning step, it has been found that the dyeing properties are improved using the same amount of dye as in the known process or that we got the same shade of coloring using a quantity

less dye.

  Theoretical aspect or how the polymer dispersion reduces exhaustion

  chromium outside the leather remains to be established.

  However, the fixation of chromium in leather, ensured by using the polyamide dispersion of the present invention, is increased up to 95%,

7 2 6 2 1 0 50

  thus ensuring the advantages mentioned above

  above. Without implying any limitation or restriction, it is believed that this increased chromium uptake and the advantages mentioned above can be attributed to

reasons described below.

  Chromium tanning is a crosslinking reaction between carboxyl groups of collagen molecules and the chromium salt. The

  protein from hides and skins can be

  as a coordinat. When ionized, the carboxyl group is attracted to the complex

  chrome tanning and a reaction is triggered.

  The fixation of chromium by the protein increases as the ionization of the carboxyl groups of the protein of hides and skins progresses and this fixation rises from 0 at a pH below 3, up to a maximum at a pH of 4. Since the polymer dispersion of the present invention also consists of the same reactive groups as those of the protein molecule, ie carboxyl groups

  and amino, these groups are likely to react

  smells exactly the same with chrome.

When chrome tanning, four

  concurrent reactions take place simultaneously.

  All these reactions are reactions between ligands on the chromium complex. The relative predominance of each reaction is controlled by adjusting the pH, temperature and

concentration.

  The four reactions are as follows: 1. The reaction between the OH group and the chromium, that is to say the basicity: 2 6 2 l v v 0 +2 (OH) (1) -

+3 - (I1)

  Cr + + OH- (Cr) 2. The reaction between the cation of the chromium compound and the sulfate +2

(OH) (OH) 0

  (|) + So: = (I) (Cr) (+ Cr (I) (so4) 3. The reactivity of masking agents such as formates

(OH) (OH) +

() ()

(+) + formate -, ê () + SO =

() ()

(Cr) (Cr)

(/) (/)

  SO4) (formate) 4. The reactivity of the protein of hides and skins

OH OH OH

()

  (Cr) + O0C- Cr (/) / \ (formate) formate OOC0 protein of hides and skins hides and skins or

OOC - polyamide -

  OP ou.-OCr-OOC-polyamide-NHCO both hides and skins formate 9g 2621050 At a low pH, the concentration of the hydroxyl group in the solution is low and the same is true for basicity or chromium concentration. The first reaction takes place as the pH rises. The chromium salt solution penetrates freely through the leather at a low pH. Since the dispersion of the present invention contains a particulate polymer of low granularity, it also penetrates through the microstructure of the leather. Therefore, the presence of the polymer dispersion constitutes a source of additional carboxyl groups for the formation of a complex. The coordination of a sulfate is not strongly influenced by the pH and the sulfate will be present in the complex at a low pH. The second reaction is not directly influenced by the pH, since SO4 is a strong ion and retains its reactivity with the protein over a wide pH range for tanning carried out in practice. Masking agents can be coordinated with chromium at a low

  pH, provided they are sufficiently ionized.

  This action depends on the nature of the acidic pH, since higher pHs favor reactivity. At low pH, the protein in hides and skins has very low reactivity with chromium. The carboxyl groups of the protein in the dispersion react in the same way as a weak acid and they

  are more influenced by the change in pH.

  As the pH rises, basicity increases

  and more OH groups are involved

  nent in the complex. At this point, the agents

  masking remain coordinated with chrome.

  The reactivity of the protein increases considerably

  as the pH rises and then

  that the initial tanning reaction is carried out.

  The presence of carboxyl groups in the dispersion facilitates the formation of a larger complex with chromium. Therefore, it is believed that instead of the chromium / protein reaction, the reaction takes place between carboxyl groups of the dispersed chromium / protein complex and that a voluminous molecular structure is obtained, which contributes to more fully filling the structure while at the same time the structure

  thus crosslinked increases the robustness of the leather.

  Leather becomes richer without losing its robustness

  tesse or its superficial characteristic. In fact, observations show that one obtains both an improvement in the properties and possibly also an increase in the surface characteristic. In addition, when the polymer consists of a polyamide, the unused amino group intervenes in the interaction with the dyes and one obtains

  an intense and tone-on-tone coloring effect.

  The types of polya-based materials

  mides which can be used in the process of the present invention are chosen from materials such as Nylon 6, Nylon 66, Nylon 10, Nylon 7, Nylon 11, Nylon 12

  or mixtures of two or more of these materials.

  Among other suitable materials there are also copolymers or terpolymers containing lactams or dibasic acids and mixed diamines. Waste or nylon fibers also constitute another source of material of this type. In the same way,

  fibers, fragments or waste of poly-

  esters may constitute certain sources of polyesters which should be used in the dispersion. Similarly, in this dis-

  persion, we can use a mixture of a poly-

ester and a polyamide.

  The concentration of the polymer in the dispersion is considered neither critical nor important for obtaining the desired properties. However, if the dispersion has a solids content greater than 50%, it can

be too viscous.

  The required aqueous dispersion of a polyamide is obtained by subjecting it to a hydrolysis step with an excess of mineral acid at temperatures of 50 to 150 C. The hydrolysed material is washed with water. The material having a pH of 2 to 8, preferably 2 to 4.5, is subjected to an attrition step, while keeping it in water in order to obtain a fine dispersion of the polymer in water. , the particles of the polymer contained in this suspension having a granularity of 2 microns and less. They are

  proved that such a preparation process without addi-

  tion of a blowing agent gave a dispersion

  containing the granular particulate polymer

cited above.

  The invention will be described below in more detail with reference to the following examples in which Examples 1-3 describe the

  process for the preparation of a microcrystalline polyamide

  tallin. Example 4 relates to the preparation of a microcrystalline polyester, while Examples 5 to 12 relate to the use of the dispersion of a polyamide for the treatment of leather. Although Examples 5 to 12 relate only to a dispersion of a polyamide, it is understood that similar results are obtained using a dispersion of a polyester. In addition and for the sake of brevity, the examples are limited only to certain types of manufactured leathers, it being understood that this process can just as easily be applied to other

types of leathers manufactured.

  The invention will now be described

by the following examples.

EXAMPLE 1

  Preparation of microcrystalline polymers

from Nylon-6.

  In a 10 liter round bottom flask fitted with a variable speed stirrer, a reflux condenser, a

  temperature control and a heating system

  6,000 ml of 10% hydrochloric acid were charged. Next, 3.600 g of nylon (polyamide) fragments having

  a viscosity molecular weight of 20,000.

  While stirring the mass at 100 revolutions / minute, the temperature of the

  balloon at 75 C + 2 C. We maintained this tempe-

  cross off for a period of 8 hours. Loose-

  The hydrolysis reaction was evaluated by crushing the fragments between the fingers or between two glass slides. The material obtained was discharged into a centrifuge. Unreacted HCl was removed and the fragments were washed until they were acid free. Neutralized fragments were analyzed for relative viscosity, molecular weight, and groups

carboxyl and amino terminals.

  Washed fragments were subjected to attrition in a friction mill. Demineralized water was added to adjust the grinding viscosity. For example, for 1 kg of wet fragments, 1.5 kg of demineralized water was added. The mill was operated by friction at 200 revolutions / minute for almost 2 hours. After attrition, another 0.5 kg of water was added, mixed well, and then sieved through a sieve

  100 mesh to eliminate the grinding media.

  The polymer obtained was characterized by its molecular weight, its relative viscosity,

  as well as by analysis of its terminal groups.

  The results obtained are indicated below: Molecular weight 4,200

Relative viscosity (solu-

  1% in H2SO4 96%) 1.35 + 0.05 NH2 group 0.25 COOH group 0.25 Density 1.14

EXAMPLE 2

  Polymer obtained from Nylon 66: The frag-

  They had a relative viscosity of 2.70 and a viscosity average molecular weight of 18,000. For the hydrolysis, the same process was followed as that described in Example 1. 3.6 kg of nylon 66 fragments were loaded into the reaction vessel containing 6 liters of 10% HCl. The container was heated to 75 ° C and the reaction was carried out for 6 hours. We unloaded the fragments. The acid was removed and the fragments were washed and subjected to

14 2621050

  attrition and the dispersion obtained was analyzed. This dispersion had a content of

  20% solids with granular particles

the size less than 2 microns.

EXAMPLE 3

  Polymer obtained from a material consisting of waste nylon threads: Average molecular weight in viscosity: 22,500 Nylon threads with a relative viscosity of 3.30 were used. In equipment of the type described in Example 1, with 6 liters of 10% hydrochloric acid, 1.8 kg of compressed nylon yarn waste was hydrolyzed. We

  carried out the hydrolysis at 75 ° C. for 6 hours.

  The wire waste fragments have been washed up to

  neutrality, then they were subjected to attrition until a fine suspension was obtained. The characteristics given below were found for the suspension: Appearance Milky white Solid content 25 + 3% Granularity of the particles: lower

at 2 microns.

  Brookfield viscosity of the suspension:

8 Pa.s (8000 centipoise).

EXAMPLE-4

  Preparation of microcrystalline polymers from

of polyester polymers.

  In a 2 liter autoclave fitted with a variable speed agitator, a temperature control device and a

  heating, 100 g of poly-

  ester, 21 ml of n-propylamine, 21 ml of ethylene-

  glycol and 1.620 ml of demineralized water. Prior-

  at this load, granules were dried

  polyester at 150 C under a nitrogen atmosphere.

  The agitation speed was maintained.

  tor at 300 rpm. We wore progressive-

  The temperature at 150 ° C. The pressure prevailing inside the container was maintained at 0-8.5 × 10 5 Pa (0-8.5 kg / cm 2). This temperature and this pressure were maintained for 2 hours. At the end of the reaction, the hydrolyzed material was discharged into water under pressure and allowed to cool to room temperature. We washed it until

  neutral pH, filtered and dried.

  The yield was 80%. Polyester micro-

  The crystalline lens obtained was subjected to attrition for 6 hours. The properties of the polyester were as follows: Melting point: 237 C Color: white A dispersion prepared from microcrystalline polyester consisted of 26% (weight / weight) of solids comprising 85% of

  particles with a granularity of less than 2 microns.

  Molecular weight: 8,000 Relative viscosity: 1.41 (phenol / tetrachlorethylene = 1: 1) pH: 6-7 COOH: 0.40 g Brookfield viscosity of the dispersion: 0.265 Pa.s (265 centipoises)

EXAMPLE 5

  Use of the polymer of Example 1 as an auxiliary agent inhibiting exhaustion

  chrome in buffalo calfskin.

  The polyamide dispersion prepared in Example 1 was used in leathers during the step

chrome tanning.

  The process adopted is indicated below: Type of leather: Buffalo calf Weight of green skin: 3.750 kg After juicing: - pH of the juice:

2.5

  Chromium powder: 4% Water: 40.0% - operation carried out for minutes Dispersion of polymer from Example 1: 5.0% - operation carried out for minutes Chromium powder: 4.00 - operation carried out for minutes Sodium sulphite (4 charges): - operation carried out for 60 minutes

Basification with bicarbo-

  sodium nate: 0.5% - 4 charges pH: 4.0 The leathers were subjected to bleaching, washing and retanning processes, dyeing and processing into fatty juice, as well

  than finishing, in the usual way.

  The results of the analysis of chromium oxides according to the process of the present invention were compared with those obtained by the known process; these results are indicated below: Cr203 content in Cr203 content leather in the effluent

According to the pro-

  known yield 4.37% 1.21% According to Example 5 5.15% 0.43% These results demonstrate that a greater amount of chromium is fixed in the leather and that a lesser amount of chromium passes into the effluent when the dispersion of

polyamide in the process.

  - The properties relating to the richness, to the characteristics specific to the dyes, to the robustness and to the touch were better than those observed in the control, when the polyamide dispersion of the present was used

invention.

EXAMPLE 6

  Use of the polymer of the present invention during the re-chroming step Type of leather Buffalo calf Weight of leather 110 kg Purification: Water: 150% Sodium sulphite: * 1% Operation

Baking soda made during

  soda: 0.75% d in 60 minutes Evacuation Washing and degreasing: Water: 125% Operation performed Degreaser 1.5% J for 45 minutes Evacuation and washing Bleaching: Water: 125% Operation performed Oxalic acid: 1.5% during 60 minutes Evacuation Chromium tanning: Water: 125% Formic acid: 0.1% Dispersing agent Amphoteric operation: 0.25% for 90 minutes Chromium powder: 3.0% Polymer dispersion

  from example 1: 4.0% Operation carried out

  Fat juice: 0.3% killed during Preservative: 0.02% 90 minutes "Baysyntan CD" (BASF): 0.3%

  Anion leveling agent - Operation performed

  than: 0.3% killed during Chromium powder: 3.0% 90 minutes "Baysyntan AN" (BASF): 2.0%

  Sodium bicarbonate: 1.5% Operation performed

  killed for minutes Washing: pH 3.5 to 4 The leathers were washed, neutralized, dyed, subjected to a fatty juice treatment and finished in the usual manner. The Cr203 contents of the leathers were examined and the following results were found: Cr03 content Cr03 content Content no C203 enuenC203 in the leather in the effluent Known method 2.46 0.24 Method of Example 6 3 , 13 0.16 The above results demonstrate that a larger amount of chromium is fixed when using the polymer dispersion of the present invention, compared to the amount of fixed chromium obtained according to

the known technique.

  The finished leather treated by the process of the present invention has superior properties concerning its richness, its softness and its robustness compared to the treated leathers.

by the known method.

EXAMPLE 7

  Use of the polymer dispersion of example

  ple 1 as an auxiliary agent that inhibits chromium depletion in cow hides during the chrome tanning step Type of leather Cowhide Green skin weight: 2.200 kg After juicing: Juiced, pH 2.5 Salt of basic chromium: 3.5% of the weight of green skin - operation carried out for 60 minutes GLS: 2% - operation carried out for 15 minutes Dispersion of polymer of Example i: 2% - operation carried out for 35 minutes Sodium formate: 0.5% - operation carried out for 15 minutes Basic chromium salt: 3.5% - operation carried out for 60 minutes Water: 40% Sodium bicarbonate: 0.5 hour - operation carried out for 4 hours pH control: 3.8 Preservative: 0.2% - transaction performed

during 30 minutes.

  After basification, leather and effluent samples were taken, analyzed to determine the chromium oxide content, and compared with the results obtained according to the known process. The comparative results are as follows: Cr203 content Leather content in Cr203 in the effluent Known process 3.72 0.46 Example 7 4.86 0.74 These results demonstrate that a greater amount of chromium is fixed when the polymer dispersion of the present invention is used and the amount of chromium passing

  in the effluent is significantly reduced.

  Finished leather had properties

  concerning wealth, characteristics

  dyestuffs, robustness

  and touch it compared to the witness.

EXAMPLE 8

  Use of the polymer dispersion of example

  ple 1 as an auxiliary agent that inhibits exhaustion

  ment of chromium during the rechroming step of goat suede: Percentage. of added ingredients, calculated on

the weight of the skins after watering.

  Water: 150% - operation carried out for 30 minutes

Basic chromium salt

  that: 7% - operation performed for 30 minutes

Poly- dispersion

  mother of Example 1: 2% - operation carried out for 60 minutes

Basic chromium salt

  that: 5% - operation performed for 30 minutes

Poly- dispersion

  mother of Example 1: 2% - operation carried out for 60 minutes

  Abandonment overnight in the bath.

  The next day: agitation in a turbulent

for 15 minutes.

* Addition of sodium bicarbonate: 1.0% - operation performed

killed for 60 minutes.

  After basification, we analyzed the

  leather and effluent samples to determine

  mine the chromium content and we compared the

  results obtained with those of the known method.

  The results are indicated below: Cr203 content Content in (%) in Cr2O3%) leather in the effluent Known process 3.99 0.68 Example 8 6.63 0, 21 These results demonstrate that a greater amount of chromium is set when using the polymer dispersion of the present invention and the amount of chromium passing

  in the effluent is significantly reduced.

  Compared to the control, the finished leather has superior properties concerning the richness, the characteristics relating to the dyes, the ability to lightly touch, the coat, the robustness.

and touch it.

EXAMPLE 9

  Semi-chrome leathers for garments from leathers tanned with plant extracts using the dispersion of the present invention when

the retanning stage.

  Starting materials: tanned leathers with plant extracts with an average area of 0.418 m2 (4.5 square feet). Touch along the backbone to level the substance; Impregnation of the back 600% water 0.25% sodium lauryl sulfate, 45 minutes% water Evacuation Washing: 2 times Purification: 300% water 1% borax)% water) 15 minutes) 0.5% bicarbonate) sodium) 15 minutes sodium)% water) Washing: 300% water, 15 minutes Confit: 300% water 0.5% oxalic acid)% d (water) 15 minutes 1% formic acid, 30 minutes pH control at 3.8-4.0 Chromium tanning: 8% chromium extract) 30 minutes

30% water) + 30 minutes

  ) your + 30)) minutes Operation one hour after

latest addition.

  Basification: 1% sodium formate) 15 minutes% water) 1.5% bicarbo-) sodium nate 15 minutes + 15 10% water) minutes + 15 minutes

PH control at 3.8-4.0 -

  evacuation Washing: 300% water - 15 minutes 300% water - 15 minutes Neutralization: 250% water) 1% formate 15 minutes% water) 0.75% bicarbonate) 10% water ) 30 minutes pH: 5.5 - evacuation Washing: 300% water - 15 minutes 300% water - at 55 C - 15 minutes Retanning, dyeing 250% water at 55 C) and treatment in 2% color) 30 minutes) fatty juice 30% water - 30 minutes 2% "Baysyntan DI" (BASF) - 30 minutes% "Targotan LSI" (SANDOZ) - 40 minutes-40 minutes 4% Vernaminol juice)) ASN (Color Chem) 3% Vernol PN juice) (Color Chem)) 40 minutes 4% Vernol SS juice) (Color Chem)% water) 1% formic acid - 10 minutes% water Evacuation Paqueter overnight; stretch lightly, dry with a hook, spread sawdust, palisade, sample, touch on the flesh side

with 180 grit paper.

  Finishing: Wadding with 300 cm3 of 970 water liquid dye solution, dry. Old coating - Black pigment: 50 g smoothing: IM binder ("Color Chem"): cm "Eukasol U" binder (BASF): 50 g "Lepton FBA" wax (BASF): g Ammonia juice: 10 cm

Water: to make up to 1 liter.

  Spray two complete transverse coatings, intermediate drying. Spray of NC lacquer emulsion: 1 part on: Thinner: 1 part Spray a coating

complete transverse, dry.

Plating at 60 C and 25x 105-Pa.

  Experiment: The treatment adopted for the experiment was the same as that adopted for the known process, with the exception that% of "Targotan LSI" was replaced by 10% of the polymer dispersion

from example 1.

  The leathers were visually evaluated, subjected to tests to determine the physical properties, as well

than chemical analyzes.

The results are taken back

in the table below.

EXAMPLE 10

  Leather for clothing articles obtained from wet blue skins of sheep using the dispersion of the present invention during the retanning step. Washing 100% water) 0.2% acetic acid) 15 minutes Rechroming 50% water% chromium extract (previously basified to a basicity of 50%) - 1 hour pH control at 3.8 -4.0

Pack overnight.

  Wash Wash I - 150% water - 15 minutes Wash II - 150% water minutes. Neutralization 150% water - 15 minutes 1% Vernatan AKM minutes

10% water.

0.5% sodium bicarbonate -

  minutes + 15 minutes + 15 minutes% water pH control at 5.0-5.5 Washing 150% water - 15 minutes% water at 55 C - 15 minutes Retanning and treating 40% water at 55 C))

  Juice 6% Verna juice

  fat minol ("Color Chem")) ASN) 30 minutes) 4% Vernol juice) SS ("Color Chem") 4% Basyntan DI) (BASF)) 30 minutes% water) 1% acid formic) 5 minutes +) 10% water) 5 minutes +) 20 minutes Evacuate, pack overnight. Slightly stretch, dry with a hook, sprinkle with sawdust, palisade, toggle, touch, sprinkle and weigh (calculated on the weight of the crust). Impregnation of the back 1000% water) 1% wetting agent 60 minutes non-ionic)) - 1% ammonia) Abandon overnight Operation performed during

minutes.

  Evacuation. Washing 400% water - 15 minutes Tincture 250% water at 55 C minutes 1% ammonia 3% Vernaminol ASN juice ("Color Chem") minutes% water 2% dye - 30 minutes 20 % water 4% formic acid - 5 minutes, minutes - 20 minutes% water Evacuation, rinsing in hot water% water) 1% fatty juice 20 minutes cationic) Evacuation, pack overnight , stretch slightly, dry with a hook, spread

sawdust, fence.

  Completion 100 g of pigment paste) g of emulsion wax)

(BASF))

) g of resin binder)

(CLRI))

  g of protein binder cm of ammonia) 30 g of crushed "Eukasol" oil (BASF) 3) cm of ammonia Volume: to complete) at 1 liter Spray cross-coating 11/2, dry, spray cross-coating 1-11 / 2

for recovery.

  Top coating 1 part of emulsion of) lacquer 1 part of water) Spray a complete cross-coating, dry, tackle hot at 60 C

and at 25 × 105 Pa.

  Experiment The process adopted was the same as that of the known process, with the following modifications during retanning and treatment with fatty juice:% water at 55 ° C.% polymer dispersion

from example 1.

  6% Verna juice) minol ASN 2% juice) 120 Vernol P minutes% water) The polymer dispersion of Example 1 replaces 100% Basyntan DI 2% Basyntan DI)% water ) 30 minutes) 1% formic acid) 10% water) 5 minutes + minutes +) 20 minutes Drain, rinse, packet

overnight.

  The dyeing, finishing, etc., were the same as

those mentioned previously.

  The leathers were visually assessed, subjected to physical testing and chemical analysis; the results obtained are indicated in the

table below.

EXAMPLE 11

  Suede for shoes formed from skins

wet blue goats.

  Starting material: wet blue skins of goats of fairly good substance and free from cuts

  due to skinning and vein marks.

  Sample, weight (calculated on the weight of wet blue skins) Washing 150% water) 0.2% acetic acid) 15 minutes Rechroming 50% water)% Cr extract) (previously basified 1 hour at a basicity of 50%))) pH adjustment at 3.8-4.0)

Pack overnight.

  Wash I 150% water - 15 minutes Wash II 150% water - 15 minutes Neutralization 150% water 1% Vernatan AKM) 10% water) 15 minutes) 1% sodium bicarbonate) 15 minutes +% water) 15 minutes +) 15 minutes

PH control at 5.5.

  Evacuation Washing: 150% water - 15 minutes Washing: 150% water - 15 minutes Retanning and 60% water at 55 C treatment with 4% Lipoderm FB II) fat juice 2% Verna juice) minol ASN ("Color Chem")) 45 minutes) 1% Vernol SL juice ("Color Chem"))% water) 4% acacia extract 45 minutes% water) 4% Basyntan DI)% water) 45 minutes) 2% Syntan ACR) (Chennai Organic) 30 minutes% water)

Control exhaustion.

  If there is no exhaustion, add 1% formic acid) 5 minutes,% water 5 minutes,) 20 minutes% water) 20 minutes, evacuate, pack overnight, dry at hook spread

sawdust, palisander, effleu-

rer on the flesh side with

paper 180, 240 and 320.

Doler on the neck to level

the substance.

  Brush and weigh (calculated on the weight of

the crust).

  1,000% water at 55 C) 1% ammonia 1 hour) 1% non) ionic wetting agent)

Give up overnight.

Operation performed for 30

minutes - evacuation.

  Tincture 250% water)) 15 minutes 1% ammonia) 15 minutes 2% Vernac juice) minol ASN 2% Vernol SL juice) 30 minutes)% water 4% dye)% d '' water) 30 minutes 2% formic acid) 5 minutes,% water) 5 minutes,) 20 minutes 2% dye)% water) 30 minutes) 150% water) 0.5% d formic acid) 20 minutes Evacuate, pack overnight, stretch slightly, dry with a hook, sprinkle with sawdust, palisade, dry in a turbulent for 4 hours, cabillot. With regard to the experiment, the procedure taking place until neutralization was the same as for the control. The rest of the process was carried out as follows: The polymer dispersion of Example 1 replaces 50% of Basyntan DI and 100% of acacia extract. 30% water)) 4% Lipoderm FB II 2% Vernée juice) minol ASN) 2 hours 2% Vernol juice SL) 10% TUF salt) 2% Basyntan DI)% water) 45 minutes) 2% Syntan ACR)% water) 45 minutes)

Control exhaustion.

  If there is no exhaustion, add

% formic acid solution.

  The rest of the crusting process, back impregnation, dyeing, etc., was the same

than for the witness.

  The control and experimental leathers were visually examined, subjected to physical tests and to chemical analyzes. The results are included in the

table below.

EXAMPLE 12

  Suede for shoes from layers of wet blue buffalo split skins Starting material: layers of wet blue split buffalo skins. Doler to 1.0 mm

  substance (calculated on the weight after watering).

  Rechroming 50% water)% chromium extract 1 hour (basicity: 50%))) pH adjustment to 4.0 Wash Wash I 100% water - 15 minutes Wash II 100% water - 15 minutes Neutralization 150% water 1% Vernatan AKM)% water) 15 minutes) 1% bicarbonate of) 15 minutes, sodium) 15 minutes,) 10% water) 15 minutes

pH: 5.5.

  Wash Wash I 100% water - 15 minutes Wash II 100% water at 55 C minutes Tanning and 40% water at 55 C) treatment with 4% Vernol SF juice) 45 minutes fatty juice 4% Vernaminol juice) ASN)% water)) 8% acacia extract) 8% acacia extract)% water) 45 minutes 4% Basyntan DI)% water) 45 minutes ) 1% formic acid) 5 minutes,) 5 minutes, 10% water 5 minutes) 20 minutes

  Pack overnight, stretch lightly

  Roughly dry with a hook, spread sawdust, palisade, touch on the flesh side with 240, 320 paper. Touch on the side that has been in contact with the grain, with 180 paper. Experiment 20% water% dispersion of)) polymer of Example 1 4% Vernaminol ASN juice) 1 hour 4% Vernol SF juice% water) 2% Basyntan DI) 20% water) 45 minutes) 1% formic acid) 5 minutes,% water) 5 minutes,) 20 minutes The polymer dispersion of Example 1 replaces 100% of extract

acacia and 50% Basyntan DI.

  The rest of the process was the same as

for the witness.

  Tincture (common for both the control and the experiment) 1,000% water)) 1% non-ionic wetting agent) 1 hour 1% ammonia

Give up overnight.

Rinse for 30 minutes -

clear out

Washing: 400% water - 30 minutes.

  Tincture 250% water) 1% ammonia) 15 minutes) 1% Tamol NNO (BASF) 15 minutes% water 4% Vernaminol juice) ASN) 30 minutes)% water) 2% dye)% water) 30 minutes) 1.5% formic acid) 5 minutes, 15% water) 5 minutes, 2 minutes Discharge. Rinse in% water) 0.5% formic acid) 10 minutes) Evacuate, pack overnight, stretch, dry with a hook, spread sawdust, palisade, dry in a turbulent for

4 hours, toss.

  The table below gives the results

  relating to different properties of leathers.

  Ln o CD Inr- cm \ 0 C) s _-- BL 1. 99 9 suep ass aqoTu 8 L 8 A 8, Z. aan4uTal - - - L 9 L 9 deaj L 9 6 8 8 L 8 L naonoa 8 9 8 L 8 L 8 aonol L a LLL 8 9 assaqoT aouac1 nuuoo aouaTa nuuoo AouaTr nuuoo aouaT nuuoo 9dxa 9P90OJd -9dxa 9P900ad -gdx 9P90oaJd -gdxa 9P9OOJd ZI aldwaaddaaa

Claims (10)

  1. Improved method for treating leather by known steps, namely, tanning, rechroming, retanning and dyeing, characterized in that it comprises the step of treating the leather with an aqueous dispersion of a polyamide.   2. Improved method for the treatment of leather by known steps, namely, tanning, rechroming, retanning and dyeing, characterized in that it comprises the step which consists in treating the leather with an aqueous dispersion polyester.   3. Method according to claim 1 or 2, characterized in that the treatment with this aqueous dispersion is carried out during step tanning.   4. Method according to claim 1 or 2, characterized in that the treatment with this aqueous dispersion is carried out during step rechroming.   5. Method according to claim 1 or 2, characterized in that the treatment with this aqueous dispersion is carried out during the retanning stage.   6. Method according to claim 1 or 2, characterized in that the treatment with this aqueous dispersion is carried out during the dyeing step. 7. Method according to any one   claims 1 and 2, characterized in that   most of the polymer particles present in this dispersion have a granularity up to 2 microns.   8. Method according to claim 1 or 2, characterized in that the dispersion has a   solids content up to 50%.   9. Method according to claim 1, characterized in that the dispersion has a pH of 2 to 8, preferably from 2 to 4.5. 10. Method according to any one   claims 1 to 3, characterized in that   this dispersion is obtained by subjecting the polymer to attrition in a mill by friction.